BACU10P4 - A NEW STRUCTURE COMPOSED OF CHAINS OF EDGE-SHARED CU-4 TETRAHEDRA

A new barium copper phosphide compound, BaCu10P4, was synthesized by r eacting stoichiometric amounts of the elements at 1200 degrees C for 2 4 h, BaCu10P4 crystallizes in the monoclinic space group C2/m, with un it cell dimensions a = 23.288(4) b = 3.9070(10), and c = 9.534(2) Angs trom and beta = 92.26(2)degrees (Z = 4). The structure can be describe d as consisting of chains of edge-shared Cu-4 tetrahedral prisms that are knitted together by P atoms. The structure is related to BaCu8P4, which can be described in a similar fashion. Temperature-dependent res istivity measurements indicate that BaCu10P4 is a metal. Extended Huck el band calculations are consistent with metallic character for BaCu10 P4 through Cu-Cu interactions. Orbitals at the Fermi level show Cu-Cu bonding overlap. On the other hand, BaCu8P4 reveals extremely weak Cu- Cu interactions, but rather optimizes Cu-P bonding.